Silicone rubber compositions and long-term-stress-resistant silicone elastomers obtained therefrom

Abstract

The present invention relates to silicone rubber compositions and long-term-stress-resistant silicone elastomers obtained therefrom, which have excellent resistance to long-term dynamic mechanical stresses, and to their use.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to silicone rubber compositions and to long-term-stress-resistant silicone elastomers obtained therefrom which exhibit excellent resistance to long-term dynamic mechanical stresses, and to their use. [0003] 2. Background Art [0004] Silicone elastomers are frequently used in applications which are associated with high dynamic mechanical stresses. Examples are oscillation dampers, resonance dampers, exhaust and catalyst suspension elements, and engine mounts in automobiles. Further examples include mountings for movable parts in machine construction, peristaltic pump tubing in the medical field, diaphragms, valves, and in particular, keypads commonly used in the electronics field. To maintain the function of these silicone elastomer components, it is particularly important that the mechanoelastic properties either exhibit no change or change only slightly when dynamic mechanical stress is...

AI Technical Summary

Benefits of technology

[0015] It is therefore an object of the present invention to provide crosslinkable silicone compositions with basic constituents in such a way that, without addition of additives, the silicone elastomers obtained therefrom achieve far higher long-term stress resistances than conventional silicone elastomers.

Problems solved by technology

However, repeated dynamic mechanical stress cycles generally lead unavoidably to continually increasing mechanical fatigue and damage to all elastomer materials, and this ultimately leads to a loss of function of the elastomer component.

However, the presence of organophosphorus compounds in silicone compositions or silicone elastomers has a number of disadvantages.

For example, platinum-catalyzed addition crosslinking is inhibited, compression set is higher, thermal stability is reduced, and undesirable, and at times, toxic decomposition products are formed upon heating.

However, a disadvantage is that the preparation of the required siloxanols, which proceeds via a palladium-catalyzed hydrolysis step, is relatively complicated.

A disadvantage is the relatively complicated preparation of carbinol-functional siloxanes.

In addition, such compounds have a thixotropic effect, i.e. the flowability of the silicone composition is considerably impaired.

Furthermore, the relatively long-chain alkylene spacers in the carbinol-functional siloxane also lead to a reduction in the thermal stability.

However, additives having hydrolyzable groups can cause a massive increase in viscosity in flowable silicone compositions, which is why this method is only suitable for solid silicone rubber compositions.

However, this results in many disadvantages in terms of the performance of the silicone elastomers, for example reduced thermal stability and an increase in viscosity.

In addition, the long-term stress resistances obtainable by means of these methods no longer meet increased requirements with respect to the service time of silicone elastomer components subjected to dynamic mechanical stress.

Direct comparison with the approaches described above is not possible, since no information about the long-term stress resistance is given.

However, a direct comparison of the second approach with the first approach cannot be made, since no determination of the long-term stress resistance by means of the de Mattia test in accordance with JIS K-6301 was carried out.